![• <%!
String name[] = {“biswa”, “amit”, “sreejan”};
String getName(int i) {
return name[i];
}
%>](https://image.slidesharecdn.com/jspandxml-231213040856-3b5caad0/85/JSP-AND-XML-USING-JAVA-WITH-GET-AND-POST-METHODS-15-320.jpg)
![• getParameterNames() – It returns enumeration of all the
parameter names associated to the request.Enumeration e=
request.getParameterNames();
• getParameterValues(String name) – It returns the array of
parameter values.String[] allpasswords =
request.getParameterValues("password");
• getAttribute(String name) – Used to get the attribute
value. request.getAttribute(“admin”) would give you the value
of attribute admin.
• getAttributeNames() – It is generally used to get the attribute
names associated to the current session. It returns the
enumeration of attribute names present in session.Enumerator
e = request.getAttributeNames();](https://image.slidesharecdn.com/jspandxml-231213040856-3b5caad0/85/JSP-AND-XML-USING-JAVA-WITH-GET-AND-POST-METHODS-29-320.jpg)
JSP AND XML USING JAVA WITH GET AND POST METHODS
- 1. Unit - V
- 2. • Java Server Pages (JSP) is a server-side programming technology that enables the creation of dynamic, platform-independent method for building Web-based applications. • JSP have access to the entire family of Java APIs, including the JDBC API to access enterprise databases. • A JSP page consists of HTML tags and JSP tags. The JSP pages are easier to maintain than Servlet because we can separate designing and development. • Finally, JSP is an integral part of Java EE, a complete platform for enterprise class applications.
- 4. • Translation of JSP Page • Compilation of JSP Page • Classloading (the classloader loads class file) • Instantiation (Object of the Generated Servlet is created). • Initialization ( the container invokes jspInit() method). • Request processing ( the container invokes _jspService() method). • Destroy ( the container invokes jspDestroy() method).
- 5. • As depicted in the above diagram, JSP page is translated into Servlet by the help of JSP translator. The JSP translator is a part of the web server which is responsible for translating the JSP page into Servlet. After that, Servlet page is compiled by the compiler and gets converted into the class file. Moreover, all the processes that happen in Servlet are performed on JSP later like initialization, committing response to the browser and destroy.
- 6. • <html> • <body> • <% out.print(2*5); %> • </body> • </html>
- 8. • JSP scripting language include several tags or scripting elements that performs various tasks such as declaring variables and methods, writing expressions, and calling other JSP pages.
- 9. JSP Tag Brief Description Tag Syntax Directive Specifies translation time instructions to the JSP engine. <%@ directives %> Declaration Declaration Declares and defines methods and variables. <%! variable dceclaration & method definition %> Scriptlet Allows the developer to write free-form Java code in a JSP page. <% some Java code %> Expression Used as a shortcut to print values in the output HTML of a JSP page. <%= an Expression %> Action Provides request-time instructions to the JSP engine. <jsp:actionName /> Comment Used for documentation and for commenting out <%– any Text –%>
- 10. • <%-- Counter.jsp --%> <%-- Comment Tag --%> <%@ page language="java" %> <%-- Directive Tag --%> <%! int count = 0; %> <%-- Declaration Tag --%> <% count++; %> <%-- Scriptlet Tag --%> Welcome! You are visitor number <%= count %> <%-- Expression Tag --%>
- 11. • Directive tags provide general information about the JSP page to the JSP engine. A directive tag always starts with <%@ and ends with %>. • There are 3 types of directives: page, include, and taglib. • The general syntax for the 3 directives is: • <%@ page attribute-list %> <%@ include attribute-list %> <%@ taglib attribute-list %> • The tag names, their attributes, and their values are all case sensitive. • The value must be enclosed within a pair of single or double quotes. • A pair of single quotes is equivalent to a pair of double quotes. • There must be no space between the equals sign (=) and the value.
- 12. • A page directive informs the JSP engine about the overall properties of a JSP page. For example, the following page directives inform the JSP engine that Java will be used as scripting language in our JSP page: • <%@ page language=”java” %> • An include directive tells the JSP engine to include the contents of another file (HTML, JSP, etc) into the current file. For example: • <%@ include file=”test.html” %> • or • <%@ include file=”test.jsp” %>
- 13. • A taglib directive is used to associate a prefix with a tag library. For example: • <%@ taglib prefix=”test” uri=”taglib.tld” %>
- 14. • Declarations declare and define variables and methods that can be used in the JSP page (a JSP declaration can contain any valid Java declaration including inner classes and static code blocks. However, such declarations are rarely used). A declaration always starts with <%! and ends with %>. • For e.g.: <%! int i = 0; %> • This declares an integer variable i and initializes to 0. The variable is initialized only once when the page is first loaded by the JSP engine, and retains its value in subsequent client requests i.e. the value of i is not reset to 0 each time we access the page. It can contain any number of valid Java declaration statements. For example, the following tag declares a variable and a method in a single tag:
- 15. • <%! String name[] = {“biswa”, “amit”, “sreejan”}; String getName(int i) { return name[i]; } %>
- 16. • Scriptlets are used to embed any Java code fragments in the JSP page. • For example: <% i++; %> • Here the scriptlet tag is executed and the value of i is incremented each time the page is requested. We can use scriptlets for printing HTML statements also. For e.g.: • <%@ page language="java" %> <%! int i = 0; %> <% out.print(""); i++; out.print("The value of i is now: " + i); out.print(""); %>
- 17. • Expression tags are used as a shortcut to print values in the output HTML in a JSP page. Syntax of Expression tag is: • <%= variable %> • The expression is evaluated each time the page is accessed, and its value is then embedded in the output HTML. Unlike variable declarations, expressions must not be terminated with a semicolon. Thus, the following is not valid: <%= i; %>
- 18. Expression Explanation <%= 500 %> An integral literal <%= anInt*3.5/100-500 %> An arithmetic expression <%= aBool %> A Boolean variable <%= false %> A Boolean literal <%= !false %> A Boolean expression <%= getChar() %> A method returning a char <%= Math.random() %> A method returning a double <%= aVector %> A variable referring to a Vector object <%= aFloatObj %> A method returning a float <%= aFloatObj.floatValue() %> A method returning a float <%= aFloatObj.toString() %> A method that returns a String object
- 19. Expression Explanation <%= aBool; %> We cannot use a semicolon in an expression <%= int i = 20 %> We cannot define anything inside an expression <%= sBuff.setLength(12); %> The method does not return any value. The return type is void
- 20. • Action tags are used to provide request–time instructions to the JSP container or JSP engine. There are 7 types of action tags. The following table describes various JSP action tags: JSP Action Description Attribute Description of Attributes <jsp:forward> Used to forward a request to a target page page Specifies the URL of the target page <jsp:include> Includes a file in the current JSP page page flush Specifies the URL of the resource to be included.Specifies whether the buffer should be flushed or not. The flush value can be either true or false <jsp:useBean> Invokes and searches for an existing bean. id class scope beanNa me Uniquely identifies the instance of the bean.Identifies the class from which the bean objects are to be implemented. Defines the scope of the bean. Defines the referential name for the bean.
- 21. <jsp:getProperty> Retrieves the property of a bean or create a bean into a defined scope name property Defines the name for the bean. Defines the property from which the values are to be retrieved. <jsp:setProperty> Used to set the property for a bean name property value param Specifies a name for the bean. Defines the property for which values are to be set. Defines an explicit value for the bean property. Defines the name of the request parameter to be used. <jsp:param> Defines a parameter to be passed to an included or forwarded page name value Defines the name of the reference parameter. Defines the value of the specified parameter <jsp:plugin> Embed a Java applets or a JavaBean type code codebase Defines the type of plug-in to be included. Defines the name of the class to be executed by the plug-in.
- 22. • The general syntax of a JSP action tag is: • <jsp:actionName attribute-list /> • In this tag, actionName is one of the seven actions mentioned and attribute-list represents one or more attribute-value pairs that are specific to the action.
- 23. • Comments are used for documentation purposes but do not affect the output of the JSP page in any way. The syntax of a JSP comment is: • <%-- Anything you want to be commented --%>
- 24. • https://beginnersbook.com/2017/06/jsp-in-eclipse-ide- apache-tomcat-server/
- 25. • The JSP request is an implicit object of type HttpServletRequest i.e. created for each jsp request by the web container. • It can be used to get request information such as parameter, header information, remote address, server name, server port, content type, character encoding etc. • It can also be used to set, get and remove attributes from the jsp request scope.
- 26. • <form action="welcome.jsp"> • <input type="text" name="uname"> • <input type="submit" value="go"><br/> • </form> • welcome.jsp • <% • String name=request.getParameter("uname"); • out.print("welcome "+name); • %>
- 28. • getParameter(String name) – This method is used to get the value of a request’s parameter. For example at login page user enters user-id and password and once the credentials are verified the login page gets redirected to user information page, then using request.getParameter we can get the value of user-id and password which user has input at the login page.String Uid= request.getParameter("user-id"); String Pass= request.getParameter("password");
- 29. • getParameterNames() – It returns enumeration of all the parameter names associated to the request.Enumeration e= request.getParameterNames(); • getParameterValues(String name) – It returns the array of parameter values.String[] allpasswords = request.getParameterValues("password"); • getAttribute(String name) – Used to get the attribute value. request.getAttribute(“admin”) would give you the value of attribute admin. • getAttributeNames() – It is generally used to get the attribute names associated to the current session. It returns the enumeration of attribute names present in session.Enumerator e = request.getAttributeNames();
- 30. • HTTP is a "stateless" protocol which means each time a client retrieves a Webpage, the client opens a separate connection to the Web server and the server automatically does not keep any record of previous client request.
- 31. • few options to maintain the session between the Web Client and the Web Server • 1.Cookies • A webserver can assign a unique session ID as a cookie to each web client and for subsequent requests from the client they can be recognized using the received cookie. • This may not be an effective way as the browser at times does not support a cookie. It is not recommended to use this procedure to maintain the session
- 32. • 2. Hidden Form Fields • A web server can send a hidden HTML form field along with a unique session ID as follows − • <input type = "hidden" name = "sessionid" value = "12345"> • This entry means that, when the form is submitted, the specified name and value are automatically included in the GET or the POST data. Each time the web browser sends the request back, the session_id value can be used to keep the track of different web browsers. • This can be an effective way of keeping track of the session but clicking on a regular (<A HREF...>) hypertext link does not result in a form submission, so hidden form fields also cannot support general session tracking.
- 33. • You can append some extra data at the end of each URL. This data identifies the session; the server can associate that session identifier with the data it has stored about that session. • URL rewriting is a better way to maintain sessions and works for the browsers when they don't support cookies. The drawback here is that you will have to generate every URL dynamically to assign a session ID though page is a simple static HTML page.
- 34. • Apart from the above mentioned options, JSP makes use of the servlet provided HttpSession Interface. This interface provides a way to identify a user across. • a one page request or • visit to a website or • store information about that user • By default, JSPs have session tracking enabled and a new HttpSession object is instantiated for each new client automatically. Disabling session tracking requires explicitly turning it off by setting the page directive session attribute to false as follows − • <%@ page session = "false" %>
- 35. • This example describes how to use the HttpSession object to find out the creation time and the last-accessed time for a session.
- 36. <%@ page import = "java.io.*,java.util.*" %> <% // Get session creation time. Date createTime = new Date(session.getCreationTime()); // Get last access time of this Webpage. Date lastAccessTime = new Date(session.getLastAccessedTime()); String title = "Welcome Back to my website"; Integer visitCount = new Integer(0); String visitCountKey = new String("visitCount"); String userIDKey = new String("userID"); String userID = new String("ABCD"); // Check if this is new comer on your Webpage. if (session.isNew() ){ title = "Welcome to my website"; session.setAttribute(userIDKey, userID); session.setAttribute(visitCountKey, visitCount); } visitCount = (Integer)session.getAttribute(visitCountKey); visitCount = visitCount + 1; userID = (String)session.getAttribute(userIDKey); session.setAttribute(visitCountKey, visitCount); %>
- 37. <html> <head> <title>Session Tracking</title> </head> <body> <center> <h1>Session Tracking</h1> </center> <table border = "1" align = "center"> <tr bgcolor = "#949494"> <th>Session info</th> <th>Value</th> </tr> <tr> <td>id</td> <td><% out.print( session.getId()); %></td> </tr> <tr> <td>Creation Time</td> <td><% out.print(createTime); %></td>
- 38. <tr> <td>Time of Last Access</td> <td><% out.print(lastAccessTime); %></td> </tr> <tr> <td>User ID</td> <td><% out.print(userID); %></td> </tr> <tr> <td>Number of visits</td> <td><% out.print(visitCount); %></td> </tr> </table> </body> </html>
- 39. • Now put the above code in main.jsp and try to access http://localhost:8080/main.jsp. Once you run the URL, you will receive the following result − • Welcome to my website • Session Information Session info value id 0AE3EC93FF44E3C5 25B4351B77ABB2D5 Creation Time Tue Jun 08 17:26:40 GMT+04:00 2010 Time of Last Access Tue Jun 08 17:26:40 GMT+04:00 2010 User ID ABCD Number of visits 0
- 40. • Now try to run the same JSP for the second time, you will receive the following result. • Welcome Back to my website info type value id 0AE3EC93FF44E3C525 B4351B77ABB2D5 Creation Time Tue Jun 08 17:26:40 GMT+04:00 2010 Time of Last Access Tue Jun 08 17:26:40 GMT+04:00 2010 User ID ABCD Number of visits 1